<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <button onclick="handle()">请求</button>

    <script>
        function handle() {
            const xhr = new XMLHttpRequest();
            xhr.open('GET', 'http://localhost:3000')
            xhr.send()
            xhr.onreadystatechange = function () {
                if (this.readyState == 4 && this.status == 200) {
                    console.log(this.responseText);
                }
            }
        }
    </script>
</body>

</html>